1. Field of the Invention
This invention relates to a multi-view image display system for providing a plurality of view images having different view points to a viewer. More specifically, this invention relates to an improved multi-view image display system which is capable of providing a plurality of multi-view three-dimensional (3-D) images using a mask type of image display plate.
2. Description of the Related Art
Various methods for displaying 3-D images have been developed. For example, there are 1) a method for displaying the 3-D images on a scattered media using a laser beam being resonated in the air, 2) a method for displaying the 3-D images which are obtained from a plurality of pick-up devices arranged horizontally, in a predetermined order in consideration of space and/or time, 3) a method for displaying a stereoscopic image of an object by a depth-based sampling, 4) a method for providing a viewer with special eyeglasses using a parallax between a left eye and a right eye, and 5) a method using a human psychological effect by a very large image.
Among the above methods, the second displaying method is widely used in the art since it can be compatible with existing image systems implemented on a flat surface. This method is called an optical plate method because it employs the optical plate for forming a viewing zone. According to this method, flat images having different view points are displayed on a display device sequentially, depending on space and/or time; and then are projected on the optical plate or are viewed through the optical plate. Thus, multi-view images may be displayed in a space- or time-multiplexing manner on the display device; and the space- or time-multiplexed multi-view images may form an independent viewing zone by the optical plate, whereby the viewer can see a stereoscopic or 3-D image through the viewing zone.
When the viewer""s vision moves, an user will fix his (or her) eyes to another viewing zone by an image viewed in another view point; and therefore, the user can view the 3-D image. However, this method employs only a horizontal parallax except for a vertical parallax, wherein it adds to a stereoscopic feel a motion parallax corresponding to a parallax between both eyes. Further, this method fails to consider accommodation or convergence which is used for the both eyes to view the 3-D image in the actual world. For such reasons, the viewer""s eyes become easily tired, which results in a drawback that the user can not see the 3-D image for a long time.
In order to solve this problem, there have been proposed many methods which consider both of the horizontal parallax and the vertical parallax at a time. These methods allow the viewer to see the 3-D image with various poses such as an ordinary 2-D image monitor, thereby rendering fatigue of the eyes lower. Among the methods, holography is most widely known in the art. However, the holography has a shortcoming that it is difficult to implement electrically because it contains an enormous amount of data. Another frequently used method is an integral photography (IP). In the IP, an image of an object is first picked-up through a micro lens array. And then, the picked-up image is displayed on a flat surface display device such as a liquid crystal display (LCD) through a display plate. Thereafter, the viewer can see the displayed image through another micro lens array having similar characteristics as the micro lens array. To be more specific, in the IP, since each of lens included in the micro lens array may pick up the whole image of the object to be viewed at a given position of the array, the one micro lens array serves as a plurality of cameras arranged in 2-D (See xe2x80x9cF. Okano et al., Applied Optics, V36, pp. 1598-1603, 1997xe2x80x9d). Therefore, the IP can represent both of the horizontal parallax and the vertical parallax at a time, to thereby display a stereoscopic image. However, since the IP must record the whole image of the object through the micro lens, it is necessary to develop a display device capable of displaying the whole image of the object through the area corresponding to a diameter of the micro lens to provide a desired resolution. As a result, it is difficult to make a micro lens array having a relatively high resolution and a non-continuous image by the space between the adjacent micro lenses may incur a problem of noisy black dots in the image.
Alternatively, a pixel division method is disclosed in U.S. Pat. No. 4,829,365 issued to Eichenlaub. FIGS. 1A and 1B show diagrams of a 3-D image display system employing the pixel division method. This 3-D image display system comprises an image display mask 18 and a point light source array 19. The image display mask 18 has 8xc3x978 pixel cells, wherein each of the 8xc3x978 pixel cells has a plurality of subcells 23, as illustrated in FIG. 1B.
For the convenience of explanation, as shown in FIG. 1B, it is assumed that there are 16 images 1-16 each of which is comprised of 8xc3x978 pixels picked up by each of cameras 1-16 arranged in the form of 4xc3x974 matrix. In this case, each of the 8xc3x978 pixel cells consists of a plurality of pixels each of which is positioned in the same location in the images 1-16. For example, a pixel cell 21 disposed in row 1 and column 5 in the image display mask 18 consists of 16 pixels 1-1-5, 2-1-5, . . . , 16-1-5 disposed in same row and column as those of the pixel cell 21 in the image display mask 18, i.e., row 1 and column 5 in each of the images 1-16. Each of the pixels 1-1-5, 2-1-5, . . . , 16-1-5 is arranged in the form of 4xc3x974 matrix based on the position of a corresponding camera. These 4xc3x974 pixels, 1-1-5, 2-1-5, . . . , 16-1-5, correspond to the subcells explained above, respectively.
The mask 18 is illuminated by the point light source array 19 which is disposed over the back plane of the mask 18 and is provided with 8xc3x978 small point light sources disposed in the same arrangement as the 8xc3x978 pixel cells. Each of point light sources 20 in the point light source array 19 is arranged to locate at the center of each of the 8xc3x978 pixel cells. Apertures 22 are formed in each of the subcells 23 in the pixel cell to pass light. The position of the aperture in one subcell is determined such that light passing through it is collected at same position with lights from apertures at corresponding subcells in other pixel cells, whereby pixels corresponding to any one view point can be collected to form an image. However, since the size of each aperture 22 must be sufficiently smaller than that of each subcell to provide a resolution corresponding to the number of the pixels for each view point image, an optical efficiency is low. Also, since each of the point light sources 20 is fixed at the center of each of 8xc3x978 pixel cells, it is impossible to separate the multi-view images in the desired position by adjusting the position of each of the apertures within the subcells.
It is, therefore, a primary object of the present invention to provide a multi-view image display system which provides simultaneously a horizontal parallax and a vertical parallax as well as provides a high optical efficiency and a reliable separation of multi-view images.
In accordance with an aspect of the present invention, there is provided A multi-view image display system for providing a plurality of view images having different view points to a viewer, said plurality of view images forming individual viewing zones, respectively, and the viewing zones being arranged two-dimensionally to form a reference viewing zone, the system comprising: a point light source array having Mxc3x97N point light sources; and an image display mask disposed between the reference viewing zone and the point light source array, wherein the image display mask has Mxc3x97N pixel cells, each of said pixel cells being illuminated by each of said point light sources, wherein said each pixel cell has an image display region which is divided into a plurality of subcells arranged depending on an arrangement structure of the viewing zones, and each of said subcells transmits or reflects lights from the point light sources using a whole area of said each subcell, thereby allowing the transmitted or reflected lights to be collected in each of said viewing zones to form each of said view images.